1. Field of the Invention
The present invention relates to a piezoelectric actuator, a method of manufacturing a piezoelectric actuator, a liquid ejection head having the piezoelectric actuator, a method of manufacturing a liquid ejection head and an image forming apparatus.
2. Description of the Related Art
Japanese Patent Application Publication No. 2006-15764 discloses using a piezoelectric body formed by laminating together a piezoelectric ceramics layer and an outer side piezoelectric ceramics layer which are polarized in the thickness direction, and increasing the deformation of the piezoelectric body as a whole by coordinating shear mode deformation of the piezoelectric ceramics layer and extension mode deformation of the outer side piezoelectric ceramics layer by causing the piezoelectric ceramics layer to deform in a shear mode by generating an electric field perpendicularly to the polarization direction of the piezoelectric ceramics layer when voltage is applied, as well as causing the outer side piezoelectric ceramics layer to deform in an extension mode by generating an electric field parallel to the direction of polarization of the outer side piezoelectric ceramics layer.
U.S. Pat. No. 4,584,590 discloses an inkjet head in which a piezoelectric layer is fixed to the open end side of a pressure chamber formed in an ink jet ejector body, electrodes are formed on both surfaces of the piezoelectric layer at a position corresponding to the pressure chamber, and electrodes are also formed on both surfaces of the piezoelectric layer at a position corresponding to a peripheral position apart from the pressure chamber. In U.S. Pat. No. 4,584,590, the piezoelectric layer is polarized in the transverse direction of the layer, in such a manner that a shear mode deformation is produced in the piezoelectric layer by generating an electric field in a direction orthogonal to the direction of polarization.
The inkjet head described in Japanese Patent Application Publication No. 2006-15764 uses a piezoelectric ceramics layer in which polarization processing is carried out after forming a layer by calcination of ceramic. When the piezoelectric ceramics layer as described above is driven in shear mode, then an electric field is applied in the direction orthogonal to the direction of polarization of the piezoelectric ceramics layer, and hence there is a possibility that the polarization direction changes readily and the amount of displacement of the piezoelectric ceramics layer deteriorates. Furthermore, in the U.S. Pat. No. 4,584,590, an electric field is applied to the direction orthogonal to the direction of polarization of the piezoelectric layer. Therefore, if a piezoelectric ceramics layer is used as the piezoelectric layer, there is a possibility that the direction of polarization changes readily and the amount of displacement deteriorates. Consequently, in a piezoelectric layer formed by calcination of ceramic, it is difficult to obtain a piezoelectric actuator having high reliability.
Moreover, since the piezoelectric ceramics layer formed by calcination of ceramics has lower voltage tolerance, then it is difficult to increase the amount of displacement of the piezoelectric ceramics layer by raising the applied voltage value.